Vascular diseases, such as atherosclerosis and the like, have become quite prevalent in the modern day. These diseases may manifest themselves in a number of ways, often requiring different forms or methods of treatment for curing the adverse effects of the diseases. For example, vascular diseases may take the form of deposits or growths, also known as a stenosis, in a patient's vasculature. These deposits may restrict, in the case of a partial occlusion, or, stop, in the case of a total occlusion, blood flow to a certain portion of the patient's body. This can be particularly serious if, for example, such an occlusion occurs in a portion of the vasculature that supplies vital organs with blood or other necessary fluids.
To treat these diseases, a number of different therapies have been developed. For example, treatment devices have been developed that remove the material occluding a vascular lumen. Such treatment devices, sometimes referred to as atherectomy devices or ablation devices, use a variety of material removal means, such as rotating cutters or ablaters for example, to remove the occluding material. (The term "atherectomy device" as used in the specification refers to ablation devices for use in any portion of a patient's vasculature. Thus, while the atherectomy devices provided in accordance with preferred embodiments of the present invention are well suited for use in the coronary arteries, their use is not limited to the coronary arteries.) The material removal device, such as a rotatable burr, is typically rotated via a driveshaft that extends out of the vasculature of the patient and to an electric motor.
In operation, an ablation device is typically advanced over a guide wire placed in vivo until the material removal device is positioned just proximal to the stenosis. A motor, pneumatically driven rotor, or other similar device is used to rotate the driveshaft and the material removal device, and the material removal device is moved through the stenosis. The material removal device removes the occluding material from the vessel, rather than merely displacing or reforming the material as in a balloon angioplasty procedure.
A potentially negative characteristic for all atherectomy devices is the unwanted ablation of a vessel wall by the device. This can occur when the material removal device improperly engages the vessel wall, for example when the material removal device is not oriented substantially parallel to the axis of the vessel. In this situation, the material removal device (e.g., cutter or abrasive ablater) may engage the vessel wall and cause unwanted ablation thereto.
Similarly, unwanted ablation may also occur if undue pressure is applied to the vessel wall. More particularly, some ablative burrs are designed to differentiate between inelastic and elastic material, removing inelastic material while leaving elastic material untreated. If sufficient pressure is applied to the vessel wall, the pressure may cause the otherwise elastic tissue to become inelastic, making it more susceptible to ablation. However, as discussed above, the ablation device or burr is typically advanced over a guide wire which follows a tortuous path through the patient's vasculature. Conventional ablation devices commonly straighten the guide wire, rather than simply following the guide wire, which results in additional pressure being applied to the vessel wall.
Given the above-discussed considerations, it would be desirable to provide an atherectomy device that reduces the risk of damage to a vessel wall and/or an in vivo stent. In particular, it would be advantageous to provide an atherectomy device that aligns the burr cutting action with a path through the stenosed vessel while removing unwanted material without causing excessive pressure or wear on the vessel walls. The present invention fulfills these needs, and provides further related advantages.